Mt. Eniwa-dake (恵庭岳, Eniwa-dake) is an volcanically active mountain sitting on the northwestern shores of Lake Shikotsu-ko (支笏湖, Shikotsu-ko). Along with it's siblings Mt. Fuppushi-dake (風不死岳, Fuppushi-dake) and Mt. Tarumae-zan (樽前山, Tarumae-zan)--and indeed, the lake itself--Mt Eniwa-dake is the product of enormous volcanic activity some 40,000 years ago. This eruption--and many, many ensuing ones--have shaped the geology and scenery of the area around the lake, and perhaps nowhere is this more evident than on the western slopes of Mt. Eniwa-dake, where a lava flow dammed up the small Okotanpe River to create Lake Okotanpe-ko (オコタンペ湖, Okotanpe-ko).
Mt. Eniwa-dake's name comes from its Ainu name: e-en-iwa, meaning 'mountain with a pointed head'. From below, its summit indeed does seem to pierce the sky, giving it an instantly recognizable silhouette from miles away.
The trail runs from the huge crater of Lake Shikotsu-ko up a ridge formed by the left bank of the Porobinai-sawa Beck (ポロビナイ沢, Porobinai-sawa). Some years back, a crag along the upper part of the mountain had collapsed, so everywhere beyond No. 2 Miharashi-dai (第二見晴台, Dai-ni miharashi-dai) had been closed by the trail managers. It's possible--likely, in fact--that the trail has been reopened now; but it's always a good idea to check beforehand.
If you're traveling Hokkaido by public transit, you're in luck--there's a bus stop at the trailhead itself.
From the trailhead you'll head along a dried-up riverbed through a bright, lively forest where the climb begins in earnest. As you move away from the noise and bustle of the parking lot, the sights, sounds, and smells of the forest will bloom around you. Note the tiny white snakeberry flowers and the yellow short-stipule violets trailside in the early- to mid-summer.
You'll hit a steep slope as you move into and through a forest of the dark Sakhalin fir before coming out onto the spine of a sharp ridge. While the going might get a little tough, the trail is well-worn and ropes have been installed where some hand-and-foot scrambling is required. Altitude attained, you'll find yourself at Miharashi-dai (見晴台, Miharashi-dai), where the views will open up for the first time.
(You'll often find a Miharashi-dai or two on any given massif in Japan; the word literally translates to 'blue-sky-viewing plateau'.)
From the rocky Miharashi-dai you'll be able to see the summit up ahead of you, above the blown-out volcanic crater itself. Below you, the expansive blue waters of Lake Shikotsu-ko, shining like a giant eye. Keep climbing along Miharashi-dai, and along the rocky trail you'll see the little bell-shaped cliffbeard and Penstemon frutescens, a beautiful little pink-purple-white flower for which I can find no English name (and trust me I have tried).
Halfway between station markers 8 and 9, you'll come to the singularly named '8.5th station marker' (八・五合目, 8.5-goume) and the No. 2 Miharashi-dai, beyond which, at the time, I couldn't pass.
From here the return voyage is down the trail you came up on.
In about mid-May, the blooming of spring flowers will chase away the snow. In late June, in the forests you can see snakeberry, skeleton flower, and Japanese wood poppies; while around Miharashi-dai you’ll see clubmoss mountain heather, Penstemon frutescens, and pincushion plant, among other mountain flowers. The leaves change color from the beginning of October onward.